What Repriming Means and Why Your Pump Needs It

Repriming means refilling the pump chamber with water so it can create the suction needed to draw water up from the well. When air enters the pump—usually after the well runs dry, a pipe cracks, or you shut off the system for maintenance—the pump loses its ability to pull water. It will run but deliver nothing, or sputter and lose pressure. Repriming forces water back into the pump so it can work again.

The process takes 15 to 30 minutes and requires only a bucket of water and basic tools you likely have at home. You do not need to call a technician for a straightforward repriming, though if the pump will not hold prime after you finish, or if it loses prime repeatedly, the problem is usually a leak or a failing check valve—those do require professional help.

Key Takeaways

  • Turn off the pump at the breaker before you start, and wait for pressure in the tank to drop to zero on the gauge.
  • Locate the priming plug (usually a brass or plastic cap on top of the pump) and remove it to pour water directly into the pump chamber.
  • Pour water slowly until it reaches the fill line or until water comes out of the vent hole, then replace the plug and turn the pump back on.
  • If the pump runs for more than a minute without building pressure, turn it off and reprime again—air pockets sometimes need a second fill.
  • If the pump will not hold prime after two attempts, check for leaks in the suction line or a failed check valve, which require professional repair.

Turn Off Power and Release Tank Pressure

Start by switching off the pump at the circuit breaker. Do not rely on a switch at the pump itself—you need the breaker off so the motor cannot restart while you are working. Wait at least two minutes for any residual electrical charge to dissipate.

Next, open a faucet somewhere in the house and let it run until no water comes out. This drains the pressure tank and makes it safe to open the pump. Watch the pressure gauge on the tank (if you have one) and confirm it reads zero. If you do not have a gauge, straightforward run the faucet until it stops producing water.

Locate and Open the Priming Plug

The priming plug is a small cap, usually brass or plastic, on the top or side of the pump body itself—not on the tank. On jet pumps (the most common type in homes), it sits on the pump housing near where the suction line enters. On submersible pumps, you may not have a priming plug; those are sealed units and repriming requires a different approach (see the FAQ section below).

Use an adjustable wrench or the correct socket to unscrew the plug slowly. Water or air may spray out—this is normal. Have a bucket or towel ready. Once the plug is off, set it aside where you will not lose it. Do not force it; if it is stuck, explore penetrating oil and wait 10 minutes before trying again.

Pour Water Into the Pump Chamber

Fill a bucket with water from any faucet in your house. Pour the water slowly into the opening where the priming plug was. Watch for water to fill the chamber. Most pumps have a fill line marked inside, or you will see water rising toward the top of the visible chamber. Stop when water reaches that line, or when water begins to come out of a vent hole on the pump (if one is visible).

Do not overfill—excess water will just spill out and make a mess. If the pump has a vent hole and water comes out of it, that is a sign the chamber is full. Pour slowly so you can see the water level and avoid waste. This usually takes one to two buckets, depending on pump size.

Reinstall the Plug and Start the Pump

Screw the priming plug back in by hand first, then tighten it with your wrench. Do not over-tighten; snug is enough. If the plug has a rubber washer or gasket, make sure it is seated properly so the seal is watertight.

Turn the pump back on at the breaker. Listen and watch for the pressure gauge to rise. The pump should begin to build pressure within 30 seconds. You may hear air hissing out of faucets in the house as the system fills—this is normal. Let the pump run until the pressure gauge reaches the normal operating range (usually 40 to 60 pounds per square inch, depending on your system). This takes two to five minutes.

What to Do If the Pump Does Not Hold Prime

If the pump runs for more than a minute without the pressure gauge moving, or if pressure rises briefly then drops back to zero, turn off the pump when ready and reprime it again. Sometimes air pockets need a second fill to clear completely. Repeat the process: turn off the pump, open a faucet to release pressure, remove the priming plug, and pour water in again.

If the pump still will not hold prime after a second attempt, the problem is usually a leak in the suction line (the pipe that draws water from the well) or a failed check valve inside the pump. Both of these require professional repair. A leak will draw air into the system faster than the pump can push water, and a failed check valve will not hold water in the chamber when the pump stops. Do not keep running the pump—this can damage the motor. Contact a well service technician to inspect the suction line and check valve.

Common Mistakes to Avoid

Do not skip turning off the breaker. Working on a live pump is dangerous, and the motor can restart unexpectedly. Do not pour water in too fast or you may splash water into electrical connections. Do not over-tighten the priming plug—you can crack the pump housing or strip the threads.

Do not assume the pump is broken if it does not prime on the first try. Air pockets are common, especially after the well runs dry or after maintenance work. A second repriming usually solves it. Do not run the pump continuously if it will not build pressure—this overheats the motor and can cause permanent damage. If it fails twice, stop and call a technician.

Frequently Asked Questions

How do I reprime a submersible pump?

Submersible pumps are sealed units without a priming plug, so you cannot reprime them manually. If a submersible pump loses prime, the problem is usually a leak in the drop pipe or a failed check valve at the pump head. You will need a well service technician to diagnose and repair it. Do not attempt to open or disassemble a submersible pump yourself.

Can I use any water to reprime, or does it have to be well water?

Use any clean water—tap water from your house is fine. Well water is not necessary. If your house water is off, use bottled water or water from a neighbor's tap. The goal is straightforward to fill the pump chamber; the source does not matter.

Why does my pump lose prime every few weeks?

Repeated loss of prime usually means a slow leak in the suction line or a check valve that is not sealing properly. Both allow air to enter the system. Have a well technician inspect the suction line for cracks or loose fittings, and test the check valve. These are not repairs you can do yourself.

What if I cannot find the priming plug?

Check the pump manual or look for a small brass or plastic cap on the pump body itself—not on the tank. If your pump is very old or unusual, the plug may be in a different location. If you cannot locate it after a careful look, take a photo and contact a well service company; they can identify the plug location for your specific pump model.

Is it normal for air to come out of faucets after repriming?

Yes, this is completely normal. Air in the lines will hiss and sputter out of faucets for a few minutes after the pump starts. Let the pump run and the air will clear on its own. You do not need to do anything—just be patient and let the system fill.